Having been in string work most of my life, I think that there are good acoustic and performance reasons why the four-string models prevailed in the violin/viola/cello world. That said, there are compelling reasons for the five-string bass in the modern orchestra. While fivers might be somewhat scarce here in the USA, a quick look at a recent photograph of the bass section of the Berlin Philharmonic will show that they are still a factor and that they still have advantages over the four-stringer with a C extension.
I just finished a five-stringer for Paul Unger of the Fort Worth Symphony, and it was a very rewarding collaboration in rethinking what orchestral bass players might need for the 21st century. If there's any interest in kicking this can down the road a bit longer, count me in. At the rate posts have occurred in this thread, we should all have time to fully contemplate our comments. As Mae West famously said, "Anything worth doing is worth doing slowly." The bass maker's lament . . .
